RFR: DRAFT: Expand old on demand [v3]

[Kelvin Nilsen]

On Sat, 8 Apr 2023 23:45:41 GMT, Kelvin Nilsen <kdnilsen at openjdk.org> wrote:

>> Kelvin Nilsen has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Polish to facilitate code reviews
>>   
>>   Reorder some code so that it better matches original organization.
>>   Cleanup comments.
>
> src/hotspot/share/gc/shenandoah/heuristics/shenandoahAdaptiveHeuristics.cpp line 190:
> 
>> 188:           continue;
>> 189:         }
>> 190:         if  (r->age() < InitialTenuringThreshold) {
> 
> why am i not checking for !r->is_old().  investigate.

Because we do not add old regions to the candidate array during young and mixed evacuations.  Note that we have an assert below that enforces this region to be young.

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PR Review Comment: https://git.openjdk.org/shenandoah/pull/248#discussion_r1161183639